The present invention relates to a vacuum processing apparatus for making predetermined processing on a target object such as a LCD (Liquid Crystal Display) substrate, a semiconductor wafer, or the like.
In general, a vacuum processing apparatus for performing predetermined processing (such as etching or the like) on a target object such as a LCD substrate, a semiconductor wafer, or the like comprises a load lock chamber provided with a transfer arm, and a process chamber provided adjacent to the load lock chamber. Each of the chambers is set to be a predetermined vacuum condition. A target object set in the load lock chamber is transferred into the process chamber by the transfer arm, and predetermined processing is performed thereon in the process transferred. Upon completion of processing in the process chamber by the transfer arm, the target object is returned to the load lock chamber by the transfer arm.
FIG. 11 shows a conventional vacuum processing apparatus. As shown in the figure, the vacuum processing apparatus comprises a process chamber (b).
A mount stage (susceptor) (i) as a lower electrode where a semiconductor wafer W as a target object to be processed is mounted on the bottom portion of the process chamber (b). A lamp unit (p) for heating the wafer W through the mount stage (i) is provided under the mount stage (i). The lamp unit (p) comprises a plurality of halogen lamps (j) which are used as a heat source to heat the wafer W.
Above the mount stage (i), a shower head (c) as an upper electrode is provided opposing to the mount stage (i). The shower head (c) comprises a head body (e) and a porous disk (d) fixed to the head body (e) by screws (f). The shower head (c) diffuses a process gas supplied to the head body (e) through a gas supply pipe (a) from a process gas supply source to supply the gas uniformly over the wafer W mounted on the mount stage (i). When forming a film on the wafer W on the mount stage (i) by a process gas supplied through the shower head (c), for example, a high-frequency voltage is applied to the shower head (c) from a high-frequency power source so that a plasma is generated at a process space between the shower head (c) and the mount stage (i).
An exhaust path (h) is provided around the process chamber (b). An porous plate (g) used for exhaustion and provided so as to surround the mount stage (i) separates the process chamber (b) and the exhaust path (h) from each other. Four exhaust pipes (k) are connected to the exhaust path (h). The four exhaust pipes (k) are arranged at intervals of 90.degree. along the circumferential direction of the exhaust path (h) and are connected together to a forced exhaust pipe (m) provided under the process chamber (b). Therefore, the gas in the process chamber (b) flows to the exhaust path (h) through the porous plate (g) for exhaustion and is forcibly exhausted from the forced exhaust pipe (m) through the four exhaust pipes (k). If four exhaust pipes (k) are thus provided around the mount stage (i), the gas in the processing chamber (b) can be uniformly exhausted.
If four exhaust pipes (k) are arranged so as to surround the lamp unit (p) as shown in FIG. 11, there is a drawback that maintenance of the lamp unit (p) (and particularly a periodical service of replacing the halogen lamps (j)) is obstructed by the four exhaust pipes (k) and the entire apparatus is enlarged.
Meanwhile, in order to supply the process gas uniformly over the wafer W, the distance between the mount stage (i) and the porous disk (d) must be set to be small as much as possible. However, a transfer arm for transferring a wafer W into and out of the process chamber (b) comes in and out through the space between the mount stage (i) and the porous disk (d). Also, the mount stage (i) is provided with a clamp ring for clamping a peripheral edge portion of the wafer W. Further, there is a limitation to downsizing of the transfer arm and the clamp ring (or reduction of the thickness of them). Therefore, the distance between the mount stage (i) and the porous disk (d) is generally set to 18 mm.
However, if the distance between the mount stage (i) and the porous disk (d) is set to 18 mm, a process gas supplied through the porous disk (d) escapes to the outer peripheral side of the process chamber so that the process gas is not applied uniformly onto the wafer W.
In relation to the problems described above, for example, U.S. Pat. No. 4,340,462 discloses a plasma processing apparatus capable of adjusting the distance between a shower head as an upper electrode and a mount stage as a lower electrode. However, in the apparatus disclosed in the U.S. Patent, the entire shower head moves up and down (e.g., the head body (e) and the porous disk (d) integrally move up and down). Therefore, the drive mechanism has a large size, and a sealing means provided between the shower head and the process chamber to seal the process chamber from the outside is enlarged (which means a large sealing area). Therefore, the leakage rate is high and a great deal of particles are generated.